1. Field of Invention
The present invention relates to an optical recording medium. More particularly, the present invention relates to an optical disk having pits with different widths.
2. Description of Related Art
Due to the small size and the large storage capacity of the optical recording media such as compact discs (CD) or digital video discs (DVD), optical recording media are widely used for storing music, movies and so on. In addition, optical recording media have lately begun to be used as a medium for storing a large amount of information.
In general, user data are digitally recorded on the optical recording medium. The user data is recorded in the following steps. The user data are encoded to channel bits by an encoding process. The channel bits are used to form pits in tracks on a surface of the optical recording medium. Moreover, each pit is formed with a fixed width in accordance with the width of the track. The channel bits are decoded to reveal the user data according to a read-out signal produced by an optical pick-up head.
Usually, 8 bits of user data are represented by a 14-bit channel bit after the encoding process. Referring to FIGS. 1 and 2, 8-bit user data 10 is transformed into a 14-bit channel bit 20 after the encoding process. Then, the channel bit 20 is used to form pits 22 in a track on the surface of the optical recording medium; the width of each pit 22 is fixed according to the width of the track. A read-out signal 24 is produced when an optical pick-up head scans the pits 22. An intensity of the read-out signal 24 is changed when the boundary of the pit 22 is scanned, and the intensity of the read-out signal 24 remains when the surface of the optical recording medium or the bottom surface of the pit 22 is scanned. By the change of the intensity of the read-out signal 24, the channel bits 20 are decoded.
The drawback of the method of recording user data described above is that the storage efficiency is less than 1 because a 14-bit channel bit only represents 8 bits of user data. Several methods have been proposed to increase the storage capacity of the optical disk. One of the methods is to provide a larger optical recording medium for increasing the surface area thereof. Another method is provided by reducing the width of the track to form smaller pits, and a new optical apparatus with a narrower wavelength light source should be used in this method. However, the optical recording medium formed by the above methods is not compatible with the conventional optical apparatus.
The invention provides an optical recording medium with increased storage capacity.
The invention provides an optical recording medium with large storage capacity, which is compatible with conventional optical apparatuses.
In accordance with an embodiment of the invention, tracks are formed on a surface of an optical recording medium, and pits are formed in each track. Each pit is formed with at least two different widths.
Another embodiment of the invention provides an optical recording medium with tracks formed on a surface of an optical recording medium and pits formed in each track. Some pits are formed with one width, and the other pits are formed with at least two different widths.
In the invention, the storage capacity of the optical recording medium is increased by forming the pits with different widths. By the invention, it is unnecessary to use a larger optical recording medium or form an optical recording medium not compatible with the conventional optical apparatuses.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.